Stabilized camera platform system

ABSTRACT

A stabilized camera system has a roll frame formed as a parallelogram linkage and pivotably attached to a pan frame. A tilt frame is pivotably attached to the roll frame. Control circuits are provided to compensate for drift, to allow manual aiming of the camera during stabilized camera operation, and for providing rapid leveling. The stabilized camera system is compact with low moments of inertia to allow rapid movements.

This application is a Continuation of U.S. patent application Ser. No.11/735,088 filed Apr. 13, 2007, and now pending, which is a Divisionalof U.S. patent application Ser. No. 10/654,848, filed Sep. 4, 2003, andnow abandoned. These applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The field of the invention is stabilized platforms and systems forcameras. More specifically, the invention relates to gyroscopicstabilization systems for motion picture and video cameras.

In motion picture, television or video filming or recording, the camerais often supported on a vehicle, to follow an action or moving sequenceto achieve a desired camera angle or effect, or to film occupants in oron the vehicle. Various specialized camera cars, camera trucks, cranes,and dollys have been used for this purpose. In addition, specializedcamera support systems have been used to mount cameras on aircraft suchas airplanes and helicopters, and on watercraft, such as boats, floats,or buoys.

In filming or recording with motion picture or television or videocameras, it is important for the camera to be maintained in a stableposition. In the most basic form, camera stability has been achieved bymounting the camera on a tri-pod. However, when the camera itself ismounted on and moves with a vehicle, maintaining camera stability oftenbecomes difficult. For example, with a camera mounted on a camera carmoving along a roadway and filming or recording a fixed subject on theground, e.g., a building, or a subject which is also moving e.g.,another moving vehicle, the camera and the lens of the camera willnecessarily move in unintended and undesirable ways, due to variousfactors. These factors may include changes in the roadway direction orinclination, changes in the vehicle orientation, due to shiftinggravitational or inertial loads, as well as for other reasons.Undesirable movement can be especially problematic when the camera ismounted on an aircraft, where movement readily occurs along threedimensions, and where wind buffeting of the camera can be extreme. Theundesirable camera lens movement resulting from these factors reducesthe quality of the filmed or recorded images, by causing the images tobe improperly framed, or to appear jumpy or erratic.

Production time can be extremely expensive. Even relatively short,simple film or video sequences, such as a scene in a motion picture ortelevision production, or a TV commercial, generally requires largenumbers of film or video production professionals, such as directors,actors, camera crew, grips, lighting and sound personnel, prop,background set, make-up and wardrobe personnel, etc. Consequently, eventhe loss of one minute of production time can translate into hundreds orthousands of dollars in increased production costs. If special effects,stunts, large numbers of extras, animal actors, etc. are involved, costscan be even higher. Accordingly, any techniques that avoid delays infilming or re-shooting, are very advantageous.

To maintain the camera lens in a stable position in these types ofsituations, various camera stabilization systems have been proposed.Generally, these camera stabilization systems rely on gyrostabilizationand feedback techniques which detect unintended or undesirable movementof the camera, and then compensate for that movement via motors drivingthe camera platform. The term gyrostabilization here means any cameramovement compensation system using position, rate, or accelerationsensors, whether “gyroscopic” or of another type.

While these types of stabilization systems have been successfully usedin the past, various disadvantages remain. The gimbal system used inexisting stabilized camera systems, which allows the camera to pivotabout three perpendicular directions, are often large and relativelytime consuming or difficult to balance. This can restrict cameramovement and positioning and also make transport, installation andset-up (including balancing) more difficult. Moreover, existing systemsgenerally have large moments of inertia, making them relatively slowerin responding to correction forces applied by the motors. Accordingly,there is a need for a camera stabilization system which is compact,lightweight, and agile in responding to correction signals and forces.

The camera operator, cinematographer, or director will often want tomanually aim the camera, by simply grabbing the camera with the hands,and aiming it as desired. Existing camera stabilization systems, whenturned on, will automatically resist such manual movement. While thisresistance can be overcome by applying force sufficient to overcome thetorque limits of the motors in the stabilization system, this results injerky and imprecise camera movement. As a result, manually aiming orpositioning of the camera by forcibly overriding stabilization systemhas disadvantages, and generally is almost never acceptable duringfilming. On the other hand, turning the stabilization system off toperform hand or manual camera aiming or movement results in loss of allstabilization functions. With the stabilization turned off, the onlyforces holding the camera in position are the frictional forces in thevarious rotation joints. Based on the weight of the camera and otherfactors, these frictional forces may be insufficient to even hold thecamera at any desired position. In addition, due to static and dynamicfriction characteristics, achieving smooth and accurate camera movement,even with the stabilization system turned off, can be difficult orimpossible. Accordingly, there is a need for a camera stabilizationsystem which allows for smooth and accurate manual aiming.

Over longer periods of time, drift in existing camera stabilizationsystems can cause the camera to become improperly positioned. Theseverity of drift varies with the accuracy of the sensors in the system.Due to drift, under certain conditions, the camera may requirerepositioning before filming or recording is continued after a lunchbreak or other pause. This can result in delays and added productioncosts. Accordingly, there is a need for a camera stabilization systemwhich compensates for or eliminates drift.

Existing camera stabilization systems have various other disadvantagesas well, relating to backlash in the drive systems, balancing, largemoments of inertia, controls and accuracy of positioning. Accordingly,various engineering challenges remain in designing an improved camerastabilization system.

SUMMARY OF THE INVENTION

After extensive research and development, the various engineeringchallenges described above associated with stabilized camera systemshave now been overcome in a new system providing significantly improvedperformance and advantages. These advantages include a compact design,precise positioning, and improved performance features andcharacteristics.

In a first aspect, a stabilized camera system includes a roll or dutchframe pivotably attached to a pan frame. The roll or dutch frameincludes a parallelogram linkage. A tilt frame is pivotably attached tothe parallelogram linkage of the roll frame. This results in a morecompact and lightweight design. With this design, the camera system canalso be more quickly and easily installed and balanced.

In a second aspect of the invention, a manual camera aiming modeprovides electronically controllable fluid dampening headcharacteristics. Via electronic controls, the amount of dampening andinertia encountered during manual movement or aiming of the camera canbe adjusted. This allows for smooth positioning or aiming of the cameraby hand. It also allows the camera to be supported with fluid head-likecharacteristics.

In a third aspect of the invention, a camera stabilization system usesfeedback from a position sensor on the camera platform to reduce oreliminate drift. As a result, even using sensors of moderate accuracy,drift can be virtually eliminated or reduced to acceptable levels.

In a fourth aspect of the invention, a dutch or roll axis controlcircuit provides a fast to horizon control mode, for rapidly moving thecamera platform to horizontal. This feature allows the camera operatorto rapidly confirm that the camera is level relative to the horizon orthe “local horizon”.

In a fifth aspect of the invention, first and second electric motorsdrive movement of pan, roll, and tilt frames or structures. This featurereduces backlash providing greater accuracy in control and positioning.

The invention resides as well in subcombinations and subsystems of thecomponents, elements, and steps described. Additional objects, featuresand advantages will appear below. Accordingly, it is an object of theinvention to provide an improved stabilized camera system.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein the same element number indicates the sameelement in each of the views:

FIG. 1 is a side view of a camera and camera stabilization systemmounted on a camera crane.

FIG. 2 is a front and left side perspective view of the camera systemshown in FIG. 1.

FIG. 3 is a front and right side perspective view thereof.

FIG. 4 is a plan view of the camera system shown in FIGS. 2 and 3.

FIG. 5 is a left side elevation view thereof.

FIG. 6 is a front view thereof.

FIG. 7 is a schematically illustrated side view of the present camerasupport system showing alternative positions.

FIG. 8 is a front view thereof with the camera removed, for purpose ofillustration.

FIG. 9 is a schematic illustration of an automatic leveling system.

FIG. 10 is a schematic illustration of a drift compensation system.

FIG. 11 is a schematic illustration of a control signal distributionsystem.

FIG. 12 is a schematic illustration of a camera stabilization systemincluding a manual camera aiming mode function.

FIG. 13 is a schematic illustration of the manual camera aiming modecircuit used in FIG. 12.

FIG. 14 is a plan view of a control panel for use with the system shownin FIG. 12.

FIG. 15 is a perspective view of a motor assembly as used on the systemshown in FIGS. 2-8.

DETAILED OF DESCRIPTION OF THE DRAWINGS

Turning now in detail to the drawings, as shown in FIG. 1, a camera 32having a lens 34 is supported on a camera stabilization system 30 at thefront end of an arm 26 of a camera crane 20. The camera crane arm 26 ispivotably supported on a mast 24 on a mobile base 22. FIG. 1 accordinglyshows one example of the use of the camera stabilization system 30 witha camera 32. The stabilization system 30 may also be used on variousother types of platforms or supports, including camera cars, cameratrucks, camera dollys, aircraft, watercraft, and virtually any othervehicle, base or support where stabilization is desirable.

Gimbal Design

Turning now to FIGS. 2 and 3, the support system 30 includes a pan frame50 preferably formed as a hollow arcuate or curved box section. A panshaft 52 is rigidly attached (e.g., welded, bolted or pinned) to a frontsupport plate 28 of the camera crane 20 or other support vehicle orstructure. The pan frame 50 can pivot or rotate on the pan shaft 52about a pan axis 51, as shown in FIG. 2.

Referring still to FIGS. 2 and 3, a dutch or roll frame 54 is attachedto a roll collar 90 having a roll shaft 56 extending into the lower endof the pan frame 50. The roll frame 54 is pivotable or rotatable about aroll axis 55 shown in FIG. 3. The roll frame 54 preferably includes aparallelogram linkage 88 having first and second parallel links 92 and94. The back ends of the links 92 and 94 are attached to the roll collar90 with locking bolts 86. Similarly, the front ends of the roll links 92and 94 are attached to a tilt collar 100 with locking bolts 86. Thelocking bolts 86 are loosened during balancing or set-up, to properlyposition the roll frame 54. The locking bolts 86 are then tightened, atfour places, to provide a rigid connection between the roll collar 90and the tilt collar 100. The roll frame 54 requires no other internal orexternal components, such as springs, dampeners, etc.

Referring still to FIGS. 2 and 3, a tilt frame 58 has a tilt shaft 60extending into the tilt collar 100. The tilt frame 58 is pivotable abouta tilt axis 59, shown in FIG. 2. Referring to FIG. 2 and momentarily toFIG. 8, the tilt frame 58 includes an L-shaped camera platform 62. Thecamera 32 is secured onto the platform 62 via standard screws or bolts.The vertical leg of the camera platform 62, as shown in FIG. 8, extendsthrough a sleeve 64 joined to the tilt collar 100. The vertical positionof the camera platform 62 (and of the camera 32) can be adjusted byloosening sleeve bolts 66, vertically positioning the camera platform 62as desired and then tightening the sleeve bolts 66.

Referring now in addition to FIGS. 4, 5, and 6, a pair of drive motorassemblies 72, 74 is provided to drive the pan frame 50, the roll frame54, and the tilt frame 58. While the six drive motor assemblies used inthe system 30 are preferably the same, to provide a more cleardescription, each of the motors is separately referred to and numberedbased on its location and function in the system 30. Referringmomentarily to FIG. 15, a drive motor assembly 75 includes an electricmotor 76 which drives an output gear 79 through a speed reducing geartrain 78.

Referring to FIGS. 2, 3, and especially FIG. 6, the pan shaft 52 ispreferably fixed in place (e.g., bolted, welded, etc.) on the supportplate 28 and does not pivot or rotate. A pan shaft gear 70 is rigidlyattached to or part of the pan shaft 52. The pan shaft gear 70 ispreferably located within the pan frame 50, although it may also beexternal. The pan frame 50 is rotatably supported on the pan shaft 52via bearings. First and second pan motor assemblies 72 and 74 areattached to the outside of the pan frame 50. The output gear 79 of eachof the pan motor assemblies 72 and 74 engages or meshes with the panshaft gear 70. Consequently, the electric motors 76 of the pan motorassemblies 72 and 74 are positioned to exert torque on the pan frameabout the pan axis 51.

A similar design is provided for rotation about the dutch or roll axis55 and the tilt axis 59. As shown in FIGS. 3 and 5, the dutch or rollshaft 56 is rotatably supported via bearings to the lower end of the panframe 50. A roll shaft gear 80 is fixed to the pan frame 50. First andsecond roll axis motors 82 and 84 are attached to the outside of theroll collar 90. The output gear 79 of each of the roll axis motors 82and 84 is engaged with the roll shaft gear 80. Consequently, the rollaxis motors 82 and 84 are positioned to exert torque on the dutch orroll frame 54 about the dutch or roll axis 55.

In a similar way, as shown in FIG. 6, the tilt axis shaft 60 isrotatably supported on bearings in the tilt collar 100 at the front endof the roll frame 54. A tilt shaft gear 102 is irrotatably attached tothe tilt collar 100. First and second tilt motor assemblies 104 and 106are attached to the outside of the tilt collar 100. The output gear 79of each tilt motor 104 and 106 meshes with the tilt shaft gear 102.Consequently, the tilt motors 104 and 106 are positioned to exert torqueon the tilt frame 58 about the tilt axis 59. Each of the motorassemblies described 72, 74, 82, 84, 104, and 106 is preferably the sameas the motor assembly 75 shown in FIGS. 15-18. The positions of themotor assemblies and gears, whether inside or outside of the frames, isimmaterial to the invention and may be selected based on design choice.

Referring to FIG. 3, by locating the dutch or roll axis motors 82 and 84on the dutch collar 90, the stabilization system 30 is made more compactand lightweight. As the weight of the system 30 is reduced, it has lessinertia. This reduced inertia reduces the torque requirements of thestabilization system. Consequently, the system 30 can have smallermotors, use less electrical power, have less friction, and provide moreaccurate stabilization. In addition, the placement of the motors 72, 74,82, 84, 104, and 106 close to the axis of rotation 51, 55, and 59reduces the angular moment of inertia of the pan frame 50, dutch or rollframe 54, and tilt frame 58, also providing for rapid stabilizingmovements.

Preferably, the motor assemblies are powered and controlled by cables orwires extending back from the stabilization system 30 to an electronicsbox 42 containing circuitry and a power supply. A control panel or box40 is connected to the electronics box 42 preferably via cables.Alternatively, wireless connections may be used. If desired, slip ringsand/or slip-type electrical connectors or fittings can be used tominimize wind-up of the cables.

As shown in FIGS. 4, 5, and 6, to prevent excessive wind-up of thecables, a stopping or limiting mechanism 112 is provided within thesystem 30 about each of the axis. Typically, the limiting mechanism 112will allow e.g., only two or three complete 360° revolutions. Thelimiting device 112 typically includes several interlocking rings, as iswell-known in the art. A locking device 114 is also provided for eachaxis. The locking mechanism 114 is used during storage, shipment, set-upor calibration and locks each of the frames into a zero (or otherpreset) angle position. The locking mechanisms 114 are generallydisengaged when the system 30 is in use.

FIGS. 1-8 show the mechanical design of the system 30 providing variousadvantages. FIGS. 9-14 show electronic and control designs. While thesedesigns are preferably used in the system 30 shown in FIGS. 1-8, theycan also be used in many other types of camera stabilization systems.Conversely, the system 30 shown in FIGS. 1-8 may be used with any of thecircuits, features, or control modes shown in FIGS. 9-13, or it may beused with existing control systems.

Manual Aiming System

Referring to FIG. 12, a camera stabilization system or subsystem 130includes a manual aiming mode. An adder, mixer, or summator 122, manualcontrol circuit 132, amplifier 124, and sensor 126 is provided in eachseparate circuit 150, 152 and 154 for control of movement about each ofthe pan, roll, and tilt axis 51, 55, and 59. The sensor 126 ispreferably a rate sensor. Referring to FIG. 12, a separate input controldevice 120 associated with each of the pan, roll, and tilt axis circuits150, 152, and 154, provides an input signal to the summator 122. Theinput control device 120 may be a joystick, control wheel, pedal, mouse,etc.

Referring to FIG. 13, the manual aiming circuit 132 is shown within thedotted lines. For the control circuit 150, 152, and 154 associated withmovement about each axis 51, 55, and 59, a switch 134 has on and offpositions. In the off position, shown in dotted lines in FIG. 13, themanual aiming circuit 132 is disconnected or inactive, and each of thecircuits 150, 152, and 154 operates using traditional feedback control.With the switch 134 in the on position, as shown in solid lines in FIG.13, the manual aiming circuits 132 are active. Each of the manual aimingcircuits 132 includes a variable resister 138 forming a divider 136. Acapacitor 142 in combination with a second variable resistor 144 forms adifferentiator 140. The outputs from the divider 136 and differentiator140 are added in a manual aiming summator 146. The output from thesummator 146 is provided to the amplifier 124. The design of the manualaiming circuit 132 in each of the three axis circuits 150, 152, and 154,are preferably the same.

In use, the switch 134 is switched to the on position, shown in FIG. 13,when the camera operator wants to manually aim the camera 32. This is acommon event in film and video production. The camera operator willoften want to manually aim the camera (by grabbing and moving the cameraplatform or the camera itself), for various reasons, such as checking ormonitoring a camera angle, field of view, etc. Traditional camerastabilization systems act to resist this type of manual movement,because such intended movement via the hands of the camera operator areindistinguishable from unintended camera movement caused by inertial orgravitational forces associated with movement of the camera crane,motion base, or vehicle supporting the camera, wind loads, etc. Withexisting systems, when the manual aiming force applied by the cameraoperators hands exceeds the maximum torque output of the motors, thecamera platform suddenly breaks free and can be manually aimed.

This results in an abrupt jerky movement which often overshoots thedesired position, with additional time consumed in achieving the desiredcamera position. Alternatively, the stabilization system can be switchedoff entirely before manual aiming. However, in either case, smoothcamera movement, in a manual mode, is difficult or impossible toachieve. Existing camera stabilization systems either interfere withmanual aiming, by automatically resisting such movements until torquelimits are exceeded, or, when they are switched off entirely, provide nobeneficial control characteristics, with the camera platform movingentirely in response to whatever forces (inertial, gravitational, wind,hand, etc.) may be instantaneously acting on the camera platform. Theseeffects result from the fundamental basic conflicting objectives betweena camera stabilization system, which attempts to keep the camera lensaimed at a desired position, regardless of external influences, andmanual aiming where the camera operator wants to simply aim the cameramanually without interference.

Referring to FIGS. 12, 13, and 14, the divider 138 provides adjustabledampening, and the differentiator 140 provides an adjustable inertiafeel, to manual camera aiming movement. Accordingly, the manual aimingcircuit 132 provides electronically adjustable inertia and dampening forcamera movement in each of the three axes, with inertia and dampeningseparately adjustable in each axis. Of course, these features may alsobe used only on a single axis, or on two axes. If all three circuits150, 152 and 154 are used, they can be individually switched on and offas needed.

FIG. 14 shows an electronics box 42 for use with the manual aimingsystem 130. Hand controls, such as joysticks on the control box 40, areconnected to the electronics box 42. Alternatively, the electronics box42 and control box 40 may be combined into a single unit, with e.g.,joysticks mounted directly on the combined box, as shown in FIG. 12.However, preferably the electronics box 42 is a separate unit providedwith inputs from a control panel or box 40 or other remotely locatedcontrol devices, such as joysticks, wheels, pedals, a mouse, or recordedplayback media (tape, CD, etc.). The switches 134 can be separately andindependently switched on or off, to provide manual or automaticcontrol. When used, dampening and inertia are preferably adjustable viaknobs, dials, etc. 138 and 140 on the control box 40. With the manualaiming circuit 132 switched on, the system 130 provides an adjustableinertia feel to the camera platform. Manual aiming movement of theplatform is resisted by the motor assemblies 75 in a way to provide aninertia feel to the camera platform. The circuit 132 controls the motorassemblies 75 based on feedback from the rate sensors 126, in a way sothat the camera platform responds to external forces as if the camerapayload has a much greater apparent inertia. As a result, during manualaiming, if the inertia levels are turned up using the differentiator140, even large forces acting on the camera platform will produce slowerand smooth movements. This provides for smoother camera platformmovement during manual aiming. Similarly, the divider 136 providesadjustable dampening to movement of the camera platform, much likehydraulic dampening, helping to provide smooth camera platform movementeven during manual aiming.

In the manual aiming circuit 132, the divider 136 provides control ofthe motor assemblies 75 to provide resistance to camera platformmovement which is proportional to the speed or rate of camera platformmovement, i.e., dampening. The differentiator 140 in the manual aimingcircuit 132 controls the motor assemblies 175 so that they provide aresistance to camera platform movement which is proportional toacceleration of the camera platform, as detected by the sensors 126(i.e., inertia). Consequently, to the camera operator, the camera feelsand reacts as if the camera is supported on a fluid mounting head.

Drift Compensation

Camera stabilization systems typically use sensors on the cameraplatform for sensing rate or angular speed. These are typically fiberoptic rate sensors. Due to slight inaccuracies in operation of thesensors, virtually all stabilization systems have some degree of drift.Drift is unintentional movement of the camera platform over time.Consequently, over longer periods of time, for example, one hour, thecamera position can drift or move, even though the stabilization systemis operating properly. As a result, if there is a significant delay infilming or video recording (for example, a lunch break), the camera maydrift out of position. If unnoticed, this can result in errors whenfilming resumes. If the drift of the camera is noticed, it must then becorrected by repositioning the camera. In either even, drift can resultin costly loss of production time.

Referring to FIG. 10, a control system 160 is provided for reducing oreliminating drift. The system 160 includes 3 separate circuits 162, 164,and 166, for controlling drift movement in each of the pan, roll andtilt axes, similar to the system described above in connection with FIG.12. As shown in FIG. 10, the camera stabilization system with driftcontrol 160 uses conventional gyrostabilization techniques, to providethe stabilization function. Specifically, a rate sensor 126 on thecamera platform provides an output to a summator 170. Outputs from trimpotentiometers 128 and from a control device 120 are also input to thesummator 170. The sum output from the summator 170 is amplified by anamplifier 124 which drives a motor assembly 75, or pair of motorassemblies. This provides feedback gyrostabilization of the camera 32.

To reduce or prevent drift, as shown in FIG. 10, a second sensor 168 isprovided to detect movement about each axis. The sensor 168 is aposition sensor. For example, the sensor 168 may be an infraredreflective sensor mounted on the pan frame 50 and facing the pan shaftgear 70. In this way, the sensor 168 facing the teeth of the gear 70 canoptically detect incremental movement. The output from the driftposition sensor 168 is provided into the drift compensation summator170, and adds to the signals from the control device 120 and trimpotentiometer 128. Consequently, the system shown in FIG. 10 having botha rate sensor 126 and a position sensor 168 associated with each pivotaxis, is able to provide stabilization and drift control or driftcompensation.

The drift position sensor 168 for detecting drift in the roll axis ispreferably supported on the roll collar 90 and detects movementoptically via the presence or absence of reflected light from the rollshaft gear 80. Similarly, the drift position sensor 168 for detectingdrift in the tilt axis is preferably supported on the tilt frame 58 anddetects movement optically relative to the tilt shaft gear 102.

Pan Control with Tilt Speed Connection

Referring to FIG. 11, as the camera platform is pivoted about the rollaxis 55, the rate sensor 126 for the pan axis 51 requires trigonometriccompensation, since the sensor 126 is no longer horizontal. For example,if the system 30 is positioned as shown in FIG. 3, the pan axis 51 isparallel with the tilt axis 59. In this position, if the cameraoperator, using a joystick 120 tries to make a panning movement (i.e.,to have the pan frame 50 pivot about the pan axis 51), the tilt axissensor will detect this movement as an unintended deviation from thedesired lens position. The system will therefore automaticallycompensate by pivoting the tilt frame by an equal an opposite amount.The end result is no change in the lens angle, because the manualcontrol of the pan frame is cancelled out by the automatic control ofthe tilt frame. With the roll frame at any angular position betweenzero, as shown in FIGS. 2, and 90 degrees, as shown in FIG. 3, the samecancelling of manual pan movement also occurs, although to a lesserextent. For example, with the tilt frame at a angle of 30 degrees (e.g.,from horizontal), automatic movement of the tilt frame will be oppositeto and one half of pan movement (sine 30=0.5) as input by the cameraoperator. In the past, achieving desired manual pan movement, againstthe automatic counteracting movements of the tilt frame, has been leftup to the camera operator (via simultaneous manual control of the tiltframe). However, this makes camera operator's job even more difficult.As shown in FIG. 11, a compensated control circuit 180 is provided toovercome this longstanding disadvantage. An output from a roll anglesensor 182 senses the sine roll angle and provides it to a multiplier184. The pan axis control signal is also provided to the multiplier 184.The output from the multiplier 184 is provided to a correction summator186, along with the outputs of the tilt axis control device 120 and thetilt axis sensor 126. Accordingly, the output of the sensors 126 iscompensated when the camera platform on which the sensors are mounted ispositioned at a non-zero roll angle. As a result, regardless of theangular position of the roll frame, all of the frames and the camera pantogether.

Automatic Leveling System

With existing camera stabilization systems, in general, a signal from alevel sensor on the camera platform provides a reference causing thecamera platform to return to level or horizontal, whenever the controlsignal from the control 120 is zero. For example, if the input controldevice 120 is a joystick, when the joystick is released and returns tocenter, the level sensor signal causes the camera platform to return toa zero position about the roll axis. However, the camera operator maywant the camera to remain at a non-zero roll angle, even with thecontrol device 120 released and at a zero position.

In addition, if the camera platform is accelerated or decelerated, e.g.,at the end of a swinging crane arm, the level sensor signal will notaccurately return the camera platform to the zero roll angle, due toinertial effects.

Referring to FIG. 9, an automatic leveling system 190 is provided havingthree modes of operation. The modes of operation are selected using acontrol panel 40. In the off mode, the system 190 operates usingexisting techniques. When the control device 120 is moved to a zero orcenter position and has a zero output, the camera platform remains inwhatever roll or dutch angle it is in. In the normal mode of operation,the system 190 operates as described above. That is, when the controldevice 120 has a zero output (for example, a joystick released), theleveling circuit 196 causes the roll axis motor(s) assembly 75 to returnthe camera platform to a zero roll angle.

In the fast mode, when the control device 120 has a zero output, theleveling circuit 196 (a switchable/separable amplifier) causes the rollaxis motor assemblies 75 to very rapidly return the camera platform to azero roll angle or horizontal. The fast mode is preferably engaged witha push button, to rapidly level the camera about the roll axis. As shownin FIG. 9, in addition to the roll axis rate sensor 126, there is also asecond sensor 195 for sensing position or inclination. In the fast mode,the leveling circuit 196 provides an output which rapidly brings thecamera to horizontal (e.g., at 10 degrees/second), about the roll axis,when ever the output signal from the inclination sensor is above aminimum threshold. When the inclination sensor output is below thethreshold value, but is not zero, (typically with the inclination sensorsensing an inclination angle or 1,2,3,4 or 5 degrees) the circuit 196steps down to a second and slower levelling rate, such as ½degree/second, to avoid overshooting.

Gimbal Balancing

Referring to FIGS. 2-8, the term gimbal refers to the mechanical linkageof the pan, roll and tilt frames and their interconnections. In use, thecamera 32 is attached to the tilt frame 54. The vertical position of thetilt frame 54 is adjusted as desired by positioning the vertical orupright arm of the tilt frame 58 in the sleeve 64 and tightening thesleeve bolts 66. The camera is then balanced side to side or laterallyon the tilt frame and locked into position via the bolts 65 shown inFIG. 8. Balancing is continued by loosening the roll frame locking bolts86 and then moving the tilt frame 58 carrying the camera 32 side toside, until there is zero torque acting about the roll axis 55. The rollcollar 90 and roll frame 54 are then pivoted 90°, from the positionshown in FIG. 2 to the position shown in FIG. 3. The center of gravityof payload, i.e., the camera 32 is then again moved from side to sideuntil zero torque results about the roll axis 55. The locking bolts 86are then tightened. Other intermediate steps

The camera 32 can then be stabilized using any of the systems, circuits,and techniques described above in connection with FIGS. 9-14.Alternatively, existing known circuits may be used.

In comparison to previous types of systems, the system 30 shown in FIGS.1-8 provides improved convenience in balancing, has fewer pinch pointsproviding increased safety in use, and is more compact and lightweight.

Referring to FIG. 15, the motor assemblies 75 have gear trains 78including conical bevel gears. The motor assemblies 75 are compact, toreduce the moments of inertia of the frames supporting them, and toprovide a compact design. For providing movement about each axis, thepairs of motors operate on offset amplified signals. The drive signal toeach motor is the same, although they are offset from each other. Thisprovides for a linear system and reduces or avoids backlash.

By locating the pan axis motors 72 and 74 on the pan frame 50, and bylocating the roll axis motors 82 and 84 on the roll frame 54, the system30 is made more compact and with less moment of inertia. This allows formore rapid movements. The system 30 is also accordingly moreaerodynamically balanced. Consequently, there is less wind load on thesystem.

Block Switching

During balancing, all motors must be turned off. Accordingly, each timethe payload changes, for example, by changing a lens on the camera,power to all motors must be turned off and the system rebalanced.Accordingly, a block power switch 200 controlling power to all motors ispreferably provided near the camera, e.g., on the pan frame 50. Thisallows the assistant camera operator to conveniently turn off power tothe motors for balancing. The block power switch 200 preferably controlsonly power to the motors, and not to the circuitry or sensors.

Thus, novel camera stabilization systems, circuits, and methods havebeen shown and described. Various changes may of course be made withoutdeparting from the spirit and scope of the invention. The invention,therefore, should not be limited, except by the following claims, andtheir equivalents.

1. A camera head comprising: an arcuate pan frame; a roll framerotatably attached to the pan frame via a roll collar, with the rollframe comprising a parallelogram linkage; a tilt frame rotatablyattached to the roll frame via a tilt collar; wherein the parallelogramlinkage provides a rigid connection between the roll collar and the tiltcollar.
 2. The camera head of claim 1 further comprising first andsecond roll motors linked to the roll collar.
 3. The camera head ofclaim 1 further comprising first and second tilt motors linked to thetilt collar.
 4. The camera head of claim 1 further comprising first andsecond pan motors linked to a pan shaft on the pan frame.
 5. The camerahead of claim 4 further comprising a roll shaft attached to the panframe, with the pan shaft and the roll shaft at right angles.
 6. Thecamera head of claim 1 with the pan frame formed as a quarter circle. 7.The camera head of claim 1 wherein the tilt frame includes an L-shapedcamera platform.
 8. A stabilized camera system, comprising: a pan frameincluding a pan shaft aligned on a pan axis; a roll frame attached tothe pan frame via a roll collar and rotatable about a roll axisperpendicular to the pan axis; at least one pan motor linked to the panshaft; at least one roll motor linked to the roll collar; and a controlsystem linked to the at least one pan motor and the at least one rollmotor.
 9. The system of claim 8 wherein the roll frame comprises firstand second rigid, straight and parallel bars pivotally attached to eachother to form a parallelogram linkage.